Castlevania Order of Ecclesia is the third installment of Castlevania titles on the DS.
It is an action platformer with RPG elements which revolves around exploration, loot everything there is to loot and vanquish evil while you're at it.
Like most recent Castlevania titles it follows the same formula as Castlevania: Symphony of the Night.
I personally like to compare it a lot with Castlevania: Aria/Dawn of Sorrow.
Why? Aria of Sorrow introduced the Soul System.
Order of Ecclesia has something similar with a twist, called the Glyph System.